Quantity Take Off or QTO is a well known project estimating company serving to the contractors, home builders, architects, design- build firms and sub contractor trade. We are providing estimating service since 2002 with a great chronicle of success.

Wednesday, May 30, 2018

This construction article is based on various reinforced concrete design examples. You will be familiar with flexural analysis of beam.

Given below, various examples and their solutions :-Make proper calculation for the following reinforced concrete sections :-

Example 1 : The balanced steel reinforcement: The maximum steel reinforcement area for a tension-controlled and transition section per ACI code 318-11.

The location of the neutral axis and the depth of the equivalent compressive Whitney stress block for the tension-controlled section in B.

Here, the compressive strength is given as f'c = 4 ksi and yield strength is given as Fy = 60 ksi

ACI code 318-11 is followed

Example 2 : Examine the adequacy of a rectangular tension controlled section on the basis of dead and live loads.

A 10 ft long cantilever beam contains a rectangular section and reinforcement. The beam bears a dead load of 2 k/ft (along with self weight) and a live load of 1 k/ft.

The compressive strength is provided as f'c = 4 ksi and yield strength is fy = 60 ksi, verify if the beam has sufficient strength to bear the provided loads with ACI Code 318-11.

Example 3 : Work out the design moment strength and the location of the neutral axis of a rectangular section containing two rows of tension reinforcement.

b (width) is given as 13 inchesd is given as 23.5h (through depth of the section) is given as 27 inchesdt (distance from the extreme compression fibre to the location of the extreme tension reinforcement) is given as 24.5

f'c (the compressive strength) is given as 4 ksify (the yield strength) is given as 60 ksi

Example 4 : Work out the design moment strength and the position of the neutral axis of a rectangular section with compression reinforcement that yields.

Tuesday, May 29, 2018

While concreting is going on the job site, construction errors may happen because of failure to certain methods, improper practice as well as casual attitude.All of these errors do not contribute to failure or impairment of concrete, but they may provide harmful effect on the structure in due course.These errors are not present throughout new construction, but also occur throughout repair or recondition works.Given below, mostly found inappropriate finishing methods which can significantly affect the strength of flat concrete surface:a. Adding water to the surface: It is found that the water is included to the surface and it is verified with the existence of a large paint brush, together with the other finishing tools. The brush is soaked in water and water is heaved onto the surface that is already completed.b. Timing of finishing: Final finishing operations should be carried on as soon as the concrete has accommodated its initial set and bleeding does not occur. The waiting period is based on the amounts of water, cement, and admixtures in the mixture but mainly the temperature of the concrete surface. On a incompletely shaded slab, the portion in the sun will normally be prepared to finish prior to the part in the shade.c. Inclusion of cement to the surface: It is frequently performed to dehydrate bleed water so that finishing can be started and it produces a thin cement-rich coating to craze or flake off easily.e. Use of tamper: A tamper or “jitterbug” is utilized on several jobs needlessly. This tool drives the coarse aggregate far from the surface and the finishing becomes smooth. This method, however, forms a cement-rich mortar surface layer having the ability for scale or craze. A jitterbug should be un-allowed with a well designed mixture. If it is required to complete a rough mixture, a jitterbug could be useful by applying it sensibly.e. Jointing: If the joints are placed and located improperly, it may lead to cracking in flatwork frequently.

Monday, May 28, 2018

Concrete belongs to a composite material formed by cement, sand, coarse aggregate, water and chemical admixtures (if necessary). To maintain the superior quality of concrete, the materials of the concrete should be blended properly so that the quality of concrete is not impacted.A well-mixed concrete is formed on the basis of the following conditions:

• The color of the concrete should be consistent.• Admixture of all concrete materials like cement, fine aggregate, coarse aggregate and water should be uniform.• Cement paste should wrap all the surface of the aggregate.• Segregation should not happen as soon as the mixing of concrete is completed.

Hand mixing (Mixing Concrete without a Mixer): Hand mixing stands for the method of mixing the different materials of concrete by hand. Mixing concrete devoid of a mixer is suitable for small works. Mixing of materials is executed on masonry platform or flat iron sheet plates.

The hand mixing concrete is performed as follow:

• Expand the measured quantity of sand on the platform, and then unload the cement on the sand.• The sand and cement should be blended thoroughly with the help of shovels in the dry state.• The measured amount of coarse aggregate should be extended, and the mixture of sand & cement should spread on it and mixed in an exact manner.• Depression is provided at the centre of the mixed materials.

• Include 75% of the required quantity of water in the depression and blend well by the shovels.• Include the leftover amount of water and the mixing method should be carried on unless a uniform colour and consistency of concrete is procured. Time of mixing concrete should not be in excess of 3 minutes.• The mixing platform should be washed at the end of the day’s work.

Machine Mixing (Mixing Concrete with a Mixer): Machine mixing is mostly suitable for bigger projects where huge masses of concrete are necessary. The machine mixing can retain the persistent uniformity of concrete. Besides, the machine mixing can significantly reduce the mixing time. In recent times, different types of concrete mixers are available which run with petrol/diesel or electricity.

The machine mixing is performed in the following ways:

• Initially, the concrete mixer should be drenched inside of the drum.• After that Cement, sand and coarse aggregate should be arranged in the portable concrete mixer in desired ratio.• The dry materials should be blended in the mixing machine. After this, exact quantity of water should be added slowly when the machine is running.• The concrete should be blended for minimum two minutes after placing all materials in the drum.• If segregation occurs, the concrete should be remixed after unloading from the mixer.

Ready Mix Concrete: Ready Mixed Concrete (RMC) is developed in the factory or in a batching plant and supplied in a ready-to-use manner. The quality of the consequential concrete is superior as compared to the site-mixed concrete.

Less time is necessary for ready mix concrete as compared to site mixing (hand or machine mixing) and quality of concrete is also greater than the site mixing.

Friday, May 25, 2018

Compass belongs to an instrument that plays an important role to workout the direction of a survey line relative to magnetic north-south.

The magnetic north-south direction is treated as the reference direction and it is known as meridian (reference direction) and the angle among the line and the meridian is known as bearing. The compass is applied for calculating the direction of a line to simplify the surveying process significantly.

The variations among prismatic and surveyor’s compass are given below :-

Prismatic Compass

1. Graduation circle is attached to a broad type needle. Therefore, it will not revolve with the line of sight.2. A prism is situated at viewing end.3. Sighting and reading are performed concurrently.4. The magnetic needle does not perform like an index.5. The graduations are in whole circle bearing.6. Graduations are pointed inverted as its reflection is examined via prism.7. The reading is captured through a prism.8. Tripod may or may not be applied. It can be persisted with a stretched hand also.

Surveyors Compass

1. Graduation circle is attached to the box. Si, it revolves with the line of sight.2. No prism exists at viewing end except for a slit.3. It is not possible to perform sighting and viewing all together.4. Magnetic needle functions as index at the time of reading.

5. The graduations remain in quadrantal system.6. Graduations are pointed directly. They are not inverted.7. The reading is captured by directly viewing from top glass.

Thursday, May 24, 2018

The verticality works should be examined at the time of building up construction at various stages like during setting up vertical formworks of columns and transmitting levels up successive floors of multi storey structures.Some useful processes to check verticality of structure throughout building construction1. Plumb-bob technique2. Spirit level3. Theodolite4. Optical plummet1. Plumb-Bob Technique: The purpose of this technique is to make sure that constructions are plumb or vertical. It’s application is also found in surveying to set up the nadir regarding gravity of a point in space.Plumb-bob comprises of a weight with pointed tip on the bottom that is tied to the end of a string. The heavy weight will cling under gravity and produce a precise vertical line that is known as plumb line.This method is very effective for examining or managing vertical line of structural elements especially indoors like lift shaft. Besides, it is also utilized to check the verticality of foundation, walls, and columns.The plumb line or vertical line of plumb-bob is affected by wind force and the perfectness is not maintained. It is possible to minimize small to medium lateral movement of plumb-bob efficiently by moistening it in oil or water.In case the height of structural member is broad, then the string can be substituted with a long wire, but precautions should be plasticized to get rid of imposing risks to the personals functioning under.2. Spirit Level Method: This tool is used for managing verticality of small scale works; as for instance inspection of formworks and door frames. If spirit level is applied for guess verifications, then it is necessary to examine the verticality with more precise method.3. Theodolite Method: Theodolite is considerably robust instrument that is utilized to examine verticality works throughout construction providing proper preciseness.It is useful for examining or managing verticality of towers, wall, foundation and columns specially large number of columns along a one grid line.The slope can be calculated out of plumb line of the member with Theodolite in conjunction with a tape.The following methods are utilized to examine column verticality:Install the digital Theodolite to the center on a peg that is set up 500 mm from the column grid.Once the Theodolite is installed perfectly the laser beam will be activated and put it to the steel tape that is retained to the formwork.The reading of the steel tape is captured via the telescope.Capture the readings of two positions at the equivalent level on both top and bottom levels of the formwork. Any curvature on the surface is easily found by capturing two readings at the same level.4. Optical Plummet Method: It belongs to an instrument that sight directly down or directly up. Optical plummet contains an automatic compensator that considerably enhances its perfectness with regards to other methods which are applied for managing verticality.

Wednesday, May 23, 2018

Combined Pad Foundation Design Spreadsheets comprise of a series of spreadsheets which can be used for stability analysis and structural design of a combined rectangular pad foundation.The spreadsheets evaluate the loadings input by the user and work out the best possible pad size to transmit these loads into an tolerable bearing pressure into the soil.Unique Pad Sizing and Eccentricity Charts simplify the process for the designer to opt for the best pad dimensions.As soon as the pad size is set, the spreadsheets then workout the design bending moments and the necessary reinforcement in both X and Y directions for sagging and hogging. The designer can then indicate the perfect reinforcement arrangement with unique recommended reinforcement chart which demonstrates graphically the existing reinforcement arrangements to fulfil both necessary cross sectional area and spacing requirements.Then a summary page is formed and a reinforcement drawing is produced to provide the perfect reinforcement arrangements which the user has indicated.The suite comprises of a total of 4 spreadsheets :• A simple combined pad design spreadsheet to make analysis of a simple combined pad foundation depending on two axial loads where the consequential load must operate through the centroid of the base.This spreadsheet is ideal for most cases and facilitates making design rapidly for straight forward situations.• A complex integrated pad design spreadsheet that can easily analyze any combined rectangular pad foundation on the basis of axial, horizontal or moment loadings.These spreadsheets contain all the tools to design complicated issues or where close attention should be given to detail. It can deal with any size rectangular pad and rectangular columns to where space is restricted in one direction. The spreadsheet also arranges the base for being loaded eccentrically in any arrangement required by the designer.It comprises sliding analysis to rationalize any horizontal loads. It involves design charts to make brief analysis of shear and punching shear loads, and comprises of bending moment and shear force diagrams to facilitate the designer to design the reinforcement in as much detail.Both simple and complex spreadsheets are available to abide by either British Standards BS8110 & BS8004 or Eurocodes BS En 1992 & BS En 1997.Download Combined Pad Foundation Design Spreadsheetscivilweb-spreadsheets.com

Tuesday, May 22, 2018

Tendering: Tendering stands for the procedure of making an offer, bid or proposal, or revealing interest in providing respond to an invitation or request for tender. With tendering, interested contractors can send their bids to execute certain packages of construction work.Organization will look for other businesses to make response to a specific requirement, like the supply of goods and services, and will opt for an offer or tender that fulfill their requirements and offers the best value for money.

Types of tendering:

a. Competitive tenderingOpen - Selective

b. Negotiated tenderingSerial - Nominative

Open tender: Open tendering is the primary tendering procedures which are implemented by both the government and private sector. The client publishes the tender offer in the local newspaper as an advertisement. It provides the detail and essential information concerning the projected works as well as invite interested contractor to tender. In legal term such tender recognizes constitute invitation to treat, a simple request made by the employer for appropriate contractor to tender their bids or offers.

If the pre-requisite to tendering on the form of possession of the obligatory registration has been recognized in the tender notice, then the advertisement is conducted to only that specific class of the public with the stated qualifications. With the purpose of decreasing the number of enquirers, earnest money is paid in (for private project).

Unless the receipt of a bone fide tender is chosen then it will be refunded. The price is very crucial in taking the decision on which the tender or bid should be received. The benefits and drawbacks of open tender are described below:

a. It empowers any concerned contractor to submit tender. So, it provides scope for an unfamiliar contractor to bid for the work.b. The tender list becomes lengthy because too many contractors submit their tender for one job.

c. It facilitates the tender list to be created neutrally. Client will acquire the bargain possible. No favor should be provided for choosing any contractor.d. Wasteful application of source.e. Make sure that there is good competition not obliged to accept any offers.f. The interrogation can be made for public accountability may be questioned if the lowest offer is not accepted.g. Conventional method of tendering, recognized to all segment of the engineering and construction industry.h. The reputable and established contractor is not allowed unless they are compelled because of the shortage of water.

Selective tender: The objective of selective tendering is to deal with the constraints of the open tendering process. Under this method, a short list of contractor is made and they are invited to present tenders. The objective of the elective tendering is to make the quality of the received bids better, to make sure that contractors who have required experience and skill get the scope to present the required bids, owning to urgency work involved, for certain reasons of the employer, as for instance security reasons in government projects, Etc. and to make the tendering procedure more simplified and reduce the burden on the associated parties. Such list is made by the suggestions from the Client’s professional adviser having knowledge of the Contractors undertaking the work earlier or advertisement via the newspaper (pre-qualification).

Monday, May 21, 2018

The following precautions should be taken during preparation of good quality concrete:To build up a quality, durable and strong structure, the concrete that is used should contain standard quality. A good quality concrete should be stable, condensed, workable and cost-effective.The following properties should be maintained to produce a good quality concrete :-1. The quality of aggregate should have been rigid and long-lasting.2. The grading of the aggregates should be done perfectly and consistently.3. Adequate quantities of cement should included in concrete to maintain necessary strength and water-resistance capability.4. The water does not contain any organic or deleterious materials.5. The quantity of water should be maintained in such a manner so that the uniformity is retained properly.6. The proportion of water-cement should keep as minimum as possible.

7. To keep up conformity, mixing of concrete should be performed systematically.

8. To eliminate air bubbles and voids, the freshly arranged concrete should be compacted properly.

9. While transmitting the concrete to the job site, no segregation of or separation of materials should happen in concrete.

10. Concrete that is provided at the point of placing should have been homogeneous & contain right symmetry.

11. Ensure that the concrete is not thrown from a distance of high point to prevent segregation.

12. Curing of concrete should be done perfectly for minimum 28 days.

13. The temperature of concrete should be retained over the freezing point unless it gets rigid enough.

14. It should be stored in even horizontal layer having invariable thickness. Concrete should fill each section in this form.

Saturday, May 19, 2018

In order to become a successful civil engineer, the following qualities are essential :-1. TESTS OF BUILDING MATERIALS: An efficient civil engineer should be well versed with various test methods of building materials. Given below, the details of some crucial test methods :-Concrete Test: Slump test, compression test, split tensile test, soundness etc.Soil Test: Core cutter test, compaction test, sand replacement test, tri axial test, consolidation test etc.Bitumen Test: Ductility test, softening point test, gravity test, penetration test etc.2. EXAMINATION OF SOIL: Prior to build up a construction, different types of soil tests are accomplished to define the settlement and constancy of soils. Therefore, as a civil engineer, one should possess adequate knowledge with these tests to carry on at the job site.3. APPLICAIONS OF SURVEYING INSTRUMENTS: Each civil engineer should have clear conception on how to apply various surveying instruments like the total station, theodolite etc. These instruments are specifically designed for marking and measurements.4. STANDARD CODES USED IN CONSTRUCTION: Each country should contain their standard safety specifications (eg: Is Code) for construction associated works. The construction works of new buildings should abide by the rules and processes indicated in the standard codes. if not, there are chances for collapsing of the structure any time.5. BAR BENDING SCHEDULE: Bar bending schedule is a vital chart for civil engineers. It offers the reinforcement calculation of RC beam like cutting length, type of bending, the length of bending etc.6. DRAWING AND DESIGN: Drawing and design are considered as the elementary part of a running project. It offers all the necessary specifications of that project. Each site engineers should possess the quality for evaluating such drawings and designs.7. COMPUTATION AND BILLS: A civil engineer should have the skills to produce the estimation and bills in a construction project.8. QUALITY CONTROL: With proper quality control, the profit of the project is raised and the cost is decreased. Therefore, a engineer should be well versed with quality control process.9. ON SITE MANAGEMENT: A engineer should have adequate knowledge with form-work, concreting, safety measures etc.10. COORDINATION WITH LABOR: As a civil engineer, one should know how to manage the labors in a job site.

Friday, May 18, 2018

If it is required to develop a new building or refurbish surviving property, the owner should have arranged a document so that the work & other portions of the construction project can be performed systematically. Each construction project should comprise of crucial documents that generally form the part of every construction contract.In the design and construction part, various types of construction documents are utilized. Given below, some vital construction documents which should exist in every construction project.1. Contract Agreements and Contracts: It should be utilized by the contracting officer (owner) as well as the contractor. It is considered as the vital part of the contract documents.2. Statement of Work (SOW): A solid scope is very helpful throughout the bidding process and soon after throughout the construction sequence. A well-defined scope should have been utilized to define the amount of work necessary for the completion of work.3. General Conditions: This contract document will be applied to determine the obligations and rights for accomplishing any project. This type of document also involve overhead costs, what to claim and your rights.4. Special Conditions: It is normally an extension of the contract and supported with the general conditions. In this part, specific conditions and clauses to each particular project or job should be indicated. It provides special attention to particular instructions and requirements which are essential to give guidelines for executing the work in a perfect way.5. Bill of Quantities: It is developed with the list of various trades, and materials which create the part of the construction. This document may not be essential for the contracting officer.6. Drawings: In this document, there are all set of drawings which are essential to execute the part of the job. These drawings generally comprise of the latest drawings and should be under possession of the contractor before starting the project. It should contain all drawings from consultants and will compose the whole project being contracted.7. CSI MasterFormat Outline: The technical requirements are described in this document to finish, carry out and/or perform each nominal task or material being included in the construction projects. It will add intelligence to the construction drawings; indicate common standards, deviations accepted, materials accepted and the compulsory testing for all materials. Normally, specifications are formed with referencing construction standards and codes.8. Creating Construction Schedule: The construction schedule belongs to a significant piece of the document. In this part, the contracting office will be able to recognize how and when the project will be finished.9. Costs in the Construction Industry: This document includes the break-ups of all items being incorporated in the construction project.10. List of Common Types of Construction Insurance: It is treated as the vital part of the contracting officer as it will provide assurance to the owner that the contractor has the means and the financial support to execute the construction contract.

Thursday, May 17, 2018

A professional quantity surveyor is employed by the client and the contractor’s quantity surveyor. These comprise of a private practice QS who performs with an organisation in an office and instructs clients as well as develop a bill of quantities for various contractors on various projects.

In a private practice, the quantity surveyor works in tandem with various architects and clients. The other type is a contractor’s QS where his/her works for the similar contractor on various projects that they possess and is utilized to generate bills of quantities for this contractor.

Usually, quantity surveyors implement control over construction costs by making perfect measurement of the necessary work, the application of expert knowledge of costs and prices of work, labour, materials and plant required. It allows them to get a clear view of the significances of design decisions at initial phase as well as provide suggestions the employer/client accordingly.

2. Contractor’s Quantity Surveyor

A contractor’s QS role works out the daily running of building projects, estimating, contract administration and construction planning together with commercial, cost and project management.

Contractor’s quantity surveyor is liable for accomplishing the operations equivalent to those of the PQS; i.e., the computation and pricing of construction work, but particularly that actually executed by the Contractor (and the Contractor’s Sub-Contractors).

The quantity surveyor from a contractor company has to undergo additional liabilities like sub-contract formation, handling all matters associated with costs and values of the project along with payment and cash flow forecasts.

Senior Quantity Surveyor –They take ownership as well as liability for the team. He/she reports daily to the lead partner of the surveying firm.

Mechanical and Electrical Quantity Surveyor – They have to take complete responsibility for all types of mechanical and electrical works. These professionals normally specialize in big projects primarily from the end of government.

The positions will be always vacant for a quantity surveyor inside large construction firms, architecture firms, law firms, governmental agencies and construction advisory firms. Any project or firm employs QS to oversee any project and check the buildings to be in conformity with all codes.

An ideal QS should possess an accredited degree and the necessary professional certifications.

Wednesday, May 16, 2018

Concrete is strong at bearing compressive stress. Plain concrete can sustain compressive loads capably. But it is always recommended to utilize the R.С.С. columns in place of plain concrete columns in modern day structures for the following reasons :-Temperature stresses are formed in Concrete because of differences in weather. Cracks may happen for this stress. To get rid of the issue and reduce cracks, some steel is provided at the face of the concrete.Columns specifically slender columns are prone to lateral loads and moments. Sometimes, tensile stress may also build up particularly in columns at exterior boundary of the building. Steel can deal with this tensile stress.While making the design of RCC structures, the reinforcement is provided in beams to tie them securely with beams.Reinforcement is provided so that the size of the columns is not increased.Reinforcement steel improves the ductility of the member so that the structure gets the ability to withstand earthquake in a superior way.In R.C.C. columns, less area is required with regards to a plain concrete column It is found that steel can bear load m-times that of concrete of the similar area. To deal with a specific load, the section of an R.C.C. column will be much finer as compared to that of plain concrete. By applying R.С.С. columns, huge space is saved since the size of the column will be less.A minimum area of steel should be arranged in the column if any case it is necessary for bearing load or not. It is performed to withstand tensile stresses which occur because of eccentricity of loads.Two types of reinforcements are arranged in a R.C.C. column.a. Longitudinal reinforcement.b. Transverse reinforcement.Longitudinal Reinforcement: The longitudinal reinforcement comprises of steel bars which are arranged longitudinally in a column. It is also known as main steel. The properties of longitudinal reinforcement are given below:i. To distribute the compressive loads along with concrete, consequently minimizing the size of the column on the whole and parting more usable area.ii. To withstand tensile stresses which are formed because of any moment or accidental eccentricity.iii. To yield ductility to the column.iv. To lessen the impact of creep and shrinkage because of continuous constant loading applied for a long time.Transverse Reinforcement: The transverse reinforcement is arranged along the lateral direction of the column in the shape of ties spirals which cover the main steel. The function of transverse steel are as following -i. To retain the longitudinal bars in exact place.ii. To resist buckling of the main longitudinal bars.iii. To avoid diagonal tension that happens because of transverse shear formed due to any moment or load.iv. To yield ductility to the column.v. To resist longitudinal splitting or bulging from concrete by enclosing it in the core.

Tuesday, May 15, 2018

The crushed stones found alongside the railway tracks are collaboratively described as track ballast. The railway tracks are built up with steel and are supported with wooden ties (utilized earlier) or concrete rectangular slabs which are described as sleepers. Sleepers can be termed with different names like cross-tie, railroad tie etc.Railway tracks have to generally undergo heat expansion and contraction, fast movement of trains, vibrations etc. Tracks should have the strength to resist all these factors to maintain the safety and security of journey.In order to perform this, crushed stones are arranged among the sleepers (or wooden-tie) and also around the tracks. The crushed stones have the capacity to retain the wooden sleepers in exact position and they will consecutively grasp the railway tracks securely.The stones should be rough in shape as these may slide over each other while the train is passing over it. Therefore, stones containing rough edges are recommended.Crushed stones can be applied for various purposes like draining of water below and around the tracks, resist the plant growth to a specific extent as well as grasping the tracks securely even in the case of super heavy trains.Given below, the purposes & reasons for applying ballast alongside tracks—• To retain the sleepers in exact position, both laterally and longitudinally (since they sequentially retain the rails in exact position & help maintain gauge).• To disperse the load of entire moving cargo from rails in to the sub-base/formation (ground underneath the ballast).• Normally, the sharp edges of the crushed stones facilitate the particles connected with each other to allow superior load distribution.• In the example given below, observe the decline in stress from 50 N/sq.cm(at sleeper-ballast bed interface) to 5 N/sq.cm (at ballast bed-formation interface).• To suppress heat expansion & contraction (because of thermal stresses), and ground movements.• To reduce the vibrations — since ballast produces cushioning effect (thus rendering elastic property to the railway track).• The air voids which exist among the stones take up vibrations and make it at ease for the travelling passengers as well as for the residents next to tracks.• To allow drainage & resist formation of precipitation from rough weather (which facilitate lessening frost heaves & retain required shear stress in sub-base).• To get rid of weed & plant growth from beneath.• To take up much of the sounds & noises which are generated with train movements.• Each component can naturally absorb sound, and sound absorption is reciprocal to surface area.• Crushed stones contain increased surface area as compared to flat plane… thus facilitate absorbing significant amount of sound.• So, it is necessary to check the variation in sound — while train is passing on track with ballast, and when train is passing on track exclusive of ballast (i.e., in places where track is fully concreted).

Monday, May 14, 2018

This is a useful technical brief for all the civil engineers that briefly explains the concept of reinforced concrete diaphragms.To cope up with seismic loading, floor and roof systems in reinforced concrete (RC) buildings function as diaphragms to deliver the lateral earthquake loads to the vertical lateral force-resisting system (LFRS). In recent times, horizontal diaphragms are generally accepted to be rigid. Consequently, the impact of their in-plane movement concerning the vertical LFRS is ignored.A precast concrete diaphragm comprises of precast components having unnecessary cast-in-place pour strips along some or all boundaries and with or without cast-in-place topping slabs.Reinforced concrete diaphragms (related to floors and roofs) regarding a structure attach the vertical structural components (like walls and frames) collectively so that the buildings can withstand outside loads like gravity and lateral forces from seismic events or wind action.Floor diaphragms are very crucial for transmitting the forces from the structure to the lateral force defiant components which then move the forces from the structure to the ground. The magnitudes of internal forces inside concrete floor diaphragms are significantly more complicated as compared to those supposed by some basic methods which are applied in current design practice, like the Equivalent Static Analysis (ESA) method. The ESA method is mostly found in structural design.Cast-in-place, reinforced concrete slabs having standard ratios and span lengths can generally be taken as rigid diaphragms. It signifies that the lateral forces are transmitted to the components of the LFRS corresponding to their proportional rigidities. In systems where beams or ribs exist – like in wide-module, two-way joist and grillage systems – the components underneath the slab allow to harden the diaphragm even further.With adherence to the American Concrete Institute’s ACI 318, Section 12.3, diaphragms should contain enough thickness to fulfill all related strength and serviceability requirements. Normally, the thickness of a floor or roof system is initially set on the basis of the strength and serviceability requirements with respect to gravity loads. That thickness is normally enough to fulfill equivalent requirements for the combined factored load effects (gravity plus lateral) on the diaphragm.

Diaphragm Forces - There exist two primary forces in diaphragms, which are known as inertial forces from the accelerations of the floors and transfer forces which originate from incompatible deformation patterns from various lateral force countering systems inside the structure. The type of lateral force resisting systems and the geometry of the structure will state which of these forces, inertia or transfer, will lead.